The increasing demand for sustainable agricultural production has driven exploration into the use of biostimulants as tools to enhance plant performance under biotic and abiotic stress. This study investigates the impact of a formulated black walnut (Juglans nigra) extract (BWE) on the vegetative growth and stress tolerance of tomato plants (Solanum lycopersicum) under reduced rates of nitrogen (N) fertilization and root-knot nematode (Meloidogyne incognita) infection. Further experiments were conducted on arthropods, the two-spotted spider mite (Tetranychus urticae). Results demonstrated that tomato plants treated with BWE and 50% of the recommended N rate performed comparably to control plants receiving 100% N across multiple growth metrics. Additionally, BWE-treated plants exhibited reduced infection by M. incognita juveniles, suggesting a plant-mediated protective effect. The observed improvements may be attributed to a hormetic response, where low doses of bioactive compounds stimulate plant defense and growth. These findings suggest that J. nigra-based biostimulants can effectively mitigate both abiotic (nutrient limitation) and biotic herbivore stressors, supporting their potential as innovative tools for sustainable crop management
.png)
